Low field transport calculation of 2-dimensional electron gas in β-(AlxGa1−x)2O3/Ga2O3 heterostructures

Abstract

β -Gallium oxide (β-Ga2O3) is an emerging wide bandgap semiconductor with potential applications in power and RF electronic systems. Previous theoretical calculation on a two-dimensional electron gas (2DEG) in β-(AlxGa1−x)2O3/Ga2O3 heterostructures, taking only polar optical and remote impurity scattering into account, shows improved mobility compared to bulk β-Ga2O3. However, the experimental results in 2DEGs have not achieved the predicted mobility values. In this work, we perform more comprehensive calculations to study the low field 2DEG transport properties in the β-(AlxGa1−x)2O3/Ga2O3 heterostructures. A self-consistent Poisson–Schrödinger simulation of a heterostructure is used to obtain the sub-band energies and the wavefunctions in the quantum well. The phonon dispersion is calculated based on the ab initio methods under the density functional theory and density functional perturbation theory frameworks. The different scatterings that are included in the calculation are due to phonons (polar and non-polar), remote impurities, the alloy disorder, and interface roughness. We include a full dynamic screening of polar optical phonons. We report the temperature dependent low-field electron mobility as a function of 2DEG density. The overall mobility is found to be increasing with electron density with an exception at low density where the antiscreening of LO phonons reduces mobility. The effect of spacer thickness, aluminum fraction, and roughness parameters on mobility is shown to be critically important. The effect of the confinement direction on 2DEG mobility is found to be small and comparable to bulk. A comparison of calculated mobility values with experimentally reported data shows a good agreement.